A pour spout (40) for conducting fluid from a container (42) to a receptacle. The pour spout (40) includes a conduit member (44) having a first end interconnectable with the container (42) and a second end having a discharge opening (50) and a vent opening (52), and a closure member (48) positioned adjacent to the discharge opening (50). The closure member (48) is movable relative to the conduit member (44) between a first position where the discharge (50) and vent openings (52) are closed, a second position where the discharge opening (50) is open. A closure locking device (62, 82) prevents bypassing the second during movement of the closure member (48) from the first position to the third position. A vent locking device (84, 86, 90, 92, 94) prevents movement of the closure member (48) from the first position to the second position when the container (42) is tipped beyong a predetermined angle. Another device (116, 122, 124) retains sub-ambient pressure within the container (42) when closure member (48) is in the second position.